(mongodb >=1.7.0)
The MongoDB\Driver\ClientEncryption class handles creation of data keys for client-side encryption, as well as manually encrypting and decrypting values.
MongoDB\Driver\ClientEncryption::AEAD_AES_256_CBC_HMAC_SHA_512_DETERMINISTIC
Uses randomized encryption.
MongoDB\Driver\ClientEncryption::AEAD_AES_256_CBC_HMAC_SHA_512_RANDOM
Uses deterministic (queryable) encryption.